Magnetic core circuits providing fractional turns



Aug. 14, 1962 H. D. CRANE 3,

MAGNETIC CORE CIRCUITS PROVIDING FRACTIONAL TURNS Filed March 3, 1958INVENTOR. HEW/77' a (RA/Vt Patented Aug. 14, 1962 3,0495% MAGNETIC COREClRClUlTS PROVIDLNG FRACTIGNAL TURNS Hewitt D. Crane, Palo Alto, Calif.,assignor to Burroughs Corporation, Detroit, Micln, a corporation ofMichigan Filed Mar. 3, 1958, Ser. No. 718,887 3 Claims. (Cl. 340-174)This invention relates to magnetic core circuits, and more particularly,is concerned with the winding of magnetic cores to achieve theequivalent of fractional turns.

In copending application Serial No. 704,511, filed in December 23, 1957,now Patent No. 3,604,244 in the name of Hewitt D. Crane and assigned tothe assignee of the present invention, there is described an improvedcore register having a novel transfer circuit requiring no diodes orother impedance elements in the transfer loops between the magnetic coredevices in the register. Information is transferred from one core deviceto another by means of pulses of predetermined current level. By meansof a biasing arrangment on the core devices, as therein described, therange over which this current level of the transfer pulse might bevaried without materially affecting the information transfer is greatlyextended, and certain other advantages are also achieved.

As further described in copending application Serial No. 698,615 filedNovember 25, 1957, now Patent No. 2,969,- 524 in the name of David R.Bennion and assigned to the assignee of the present invention, a coreregister of the type described above can be made with unity turns ratioin the windings of the transfer loops coupling one core to the nextcore. Moreover, a. core register can be constructed with a single turnlinking each of the core elements coupled by the transfer loop in theregister. However, if bias is to be utilized to extend the range of thetransfer pulse, in the manner described in connection with thefirst-mentioned copending application, the turns in the transfer loopmust be greater than the turns in the bias winding on each of the coreelements. This means that if the transfer current is to energize boththe transfer loop and the bias winding, the use of single turns in thetransfer loop dictates that the bias windings must have less than asingle turn, i.e., fractional turns. Of course, in practice, fractionalturns as such do not exist.

By the present invention, the equivalent of fractional turns isachieved. This permits a single turn to be provided in the transferwinding, the same current to pass through the transfer winding and thebias winding, and still achieve fewer ampere-turns in the bias windingthan in the transfer winding of each core element in the register. As aresult, unity turns can be used in the transfer loop, which greatlysimplifies the winding of the core elements and gives rise to simplifiedand less expensive fabricating techniques.

In brief, the invention provides the equivalent of fractional turns on amagnetic core circuit by means of a magnetic annular core including aplurality of laminated layers. The winding providing effectivefractional turns linking the laminated core includes a plurality ofparallel single conductors, each conductor linking a correspondinglaminated layer of the core element. The number of laminated layers ofthe core element and the associated number of parallel single conductorsin the winding is determined by the fractional turn desired. Forexample, if an effective one-third turn linking the core element isrequired, then three laminated layers with three parallel conductors inthe winding are provided.

For a more complete understanding of the invention, reference should behad to the accompanying drawings, wherein:

FIG. 1 shows a magnetic core transfer circuit with bias;

' of the transfer loop linking the core.

FIG. 2 is a graphical plat of flux switched in a core element as afunction of ampere-turns linking the core and is used in explaining theoperation of the circuit of FIG. 1;

FIG. 3 is a diagrammatic showing of a core element wound in a manner toachieve the effective fractional turns according to the principles ofthe present invention; and

FIGS. 4 and 5 show alternative embodiments of the present invention.

As described in more detail in the above-mentioned copendingapplications, a binary register and transfer circuit can be constructedusing basic core elements arranged as shown in FIG. 1. This circuitincludes a pair of magnetic annular cores 10 and 10 made of ferrite orsimilar magnetic material having a square hysteresis characteristic,i.e., a material having a high flux remanence. A coupling loop 20 linksthe transmitting core 10 through an output aperture 14 to the receivingcore 10' through an input aperture 12'. Transfer of information storedin the transmitter core 10 to the receiver core 10 is effected by anAdvance current pulse by means of which a current 1 is applied to thetransfer loop 20 in the direction indicated by the arrow. The advancecurrent divides in the transfer loop into a current I passing throughthe aperture 14 of the transmitting core 10 and a current I passingthrough the aperture 12' of the receiving core 10.

It can be shown that with the flux in a given core extending in the samedirection on either side of the aperture linked by the transfer loop,the current in the branch winding linking the core must exceed a certainthreshold level before any of the flux around the core can be reversedor switched. This is shown by curve A of FIG. 2, which shows therelationship between the flux switched in the core with increase ofampere-turns in the portion Ampere-turns must exceed a threshold level Tbefore a substantial amount of flux is switched in the core.

However, if the flux on either side of the aperture initially extends inopposite directions, the current required to switch flux is greatlyreduced. This relation is shown by curve B of FIG. 2, which shows thatthe ampere-turns must only exceed a much lower threshold level T beforeflux is switched in the core. The reason is that in the latter case,flux does not switch around the core, but only switches locally aroundthe aperture.

This property is used to effect the transfer between the transmittingcore and the receiving core. The advance current I is set at a levelsuch that the ampere-turns linking the two cores is below the thresholdlevel T when the cores are both cleared with all the flux in onedirection, as indicated by the arrows in FIG. 1. As a result no flux isswitched in either core by an advance current pulse. However, if thetransmitter flux is initially set with the flux extending in oppositedirections on either side of the aperture 14, the ampere-turns linkingthe core 10 through the aperture 14 will exceed the lower thresholdlevel T, when the advance pulse is applied to the transfer loop 2% As aresult, fiux is switched by the transfer pulse in the transmitter core19. The switching of flux around the aperture 14 increases the impedanceto the flow of current I thereby increasing the portion of the advancecurrent I -As a result the ampere-turns linking the receiver core 10 isincreased above the threshold level T resulting in switching of flux inthe core 16. In this manner the fiux configuration in the receiver coreat? is not modified or modified in response to an advance current pulse,depending upon the initial flux condition of the transmitter core it).

As pointed out in the above-identified patent application by Hewitt D.Crane, bias windings may be provided on both the transmitter core 10 andthe receiver core 10', as indicated at 22 and 22 respectively. Thecurrent 3 through the bias windings is in a direction to oppose theswitching of flux in the cores in response to the advance current pulse.The effect is to increase the upper threshold level T thereby permittingthe advance current to be greatly increased.

As further pointed out heretofore in the abovementioned patentapplication, the bias windings 22 and 22' may be connected in serieswith the transfer loop 26 so as to be energized by the advance currentpulse. This has the effect of providing a moving threshold with changesin level of the advance current, so as to provide a self-compensatingeffect. Since the effective upper threshold T depends upon the amount ofbias, any change in the advance current changes the amount of bias andthereby moves the threshold. if the threshold were not moving, anincrease in advance current might result in the threshold being exceededso as to produce a swit ring of flux in the receiver core It) when itwas not dean-ed. However, with the threshold moving to a higher level asthe result of the increase in bias with the increase in advance current,a greater increase in advance current is required before the thresholdlevel can be exceeded by the advance pulse.

With the circuit arranged as thus far described, the ampere-turns in thebias winding on the transmitter core must be less than hall theampere-turns linking the aperture 14. Otherwise, the ampere-turns of thebias Winding would exceed the threshold at which flux can be switchedaround the core 10. This fact has heretofore necessitated the use ofmultiple turns in the loop linking the output aperture in thetransmitting core. To use a single turn would result in the requirementthat a fractional turn link the core by the bias winding, since thecurrent is the same in both the transfer winding and bias winding. Thepresent invention achieves the effect of fractional turns in the biaswinding.

According to one modification of the present invention, as shown in FIG.3, each of the core elements in the register, such as the core elementlit, is made of a plurality of laminated layers as indicated at 30, 32,and 34, three being shown by way of example only. The transfer loop 20includes a single turn which links the core element 10 through alignedapertures in each of the laminated layers, forming a single conductiveturn linking the output aperture 14.

The bias winding 22 is formed of three parallel branches 36, 38, and 40.Each of these branches includes a single conductor which links acorresponding one of the laminated layers of the core element throughthe central opening therein. As a result, the advance current passingthrough bias winding 22 splits equally between the plurality of parallelbranches. It will be seen in PEG. 3 that /3 of the advance current lpasses through each of the parallel branches. The net current flowingbetween the layers of the core is zero, since two parallel branches ofthe bias winding pass between each layer with current flowing inopposite directions in the two branches. As a result, the effectiveampereturns linking the entire core 10 by the bias winding 22 is /sl Theeffect is that the bias Winding appears to be a third of a turn incontrast to the single turn of the transfer winding 2 3. It should benoted that the bias winding arrangement is symmetrical so that eventhough there are parallel branch windings, no circulating currents arenormally induced in the parallel branch circuits.

The same effect of fractional turns in the bias winding, achieved inFIG. 3 by laminating the core structure, can be achieved also in a solidcore structure by providing extra apertures extending through the corematerial. The apertures may extend radially as shown in FIG. 4, or mayextend parallel to the axis of revolution as shown in Pl'G. 5. In eitherevent the resulting portions of the core to which it is divided by A6apertures, are linked by separate parallel branches constituting thebias winding. Again each of the apertures has two parallel branches ofthe bias winding passing current therethrough in opposite directions sothat the net current flow through the apertures is always zero. As aresult, only the fraction of the current passing through one of theparallel branches effectively links the core to provide the effect offractional turns in the manner described above in connection with PEG.3.

From the above description it will be recognized that a bias windinghaving effectively fractional turns linking a core element is provided.By the present invention the transfer loop may include a singie turnlinking each core, and the bias winding and transfer loop winding can beconnected in series from the same current source, and yet the biaswinding can have effectively fewer ampereturns than the transfer loop,i.e., can effectively be a fraction of a turn.

While the invention has been described as including parallel branches ofsingle conductors in the bias winding, the para lei branches may be madewith several turns, and the number of turns in the different parallelbranches may not necessarily be equal. However, if they are not equal,an unbalance may exist which may produce circulating currents duringtransient periods in which flux is being switched in the core element.

What is claimed is:

l. A magnetic storage and transfer circuit comprising a magnetic coreforming a closed loop magnetic path, a portion of the core defining aplurality of parallel flux paths, a first winding and a second windinglinking different portions of the magnetic core, said windings beingconnected in series with each other across a common current source, thefirst winding including a single conductor in a single turn linking aportion or" the core, and the second Winding including a plurality ofparallel-connected single conductors, each of the conductors linking adifferent one of the parallel flux paths of the core in a single turn.

2. Apparatus as defined in claim 1 wherein the magnetic core islaminated to form the plurality of parallel flux paths, the conductorsconnected in parallel to form the second winding linking respectivelythe laminated layers of the core.

3. Apparatus as defined in claim 1 wherein the magnetic core has aplurality of apertures extending therethrough lying substantially in acommon plane extending normally to the magnetic path of the core fordividing the core into parallel flux paths in the regions between theapertures, the single conductor of the second winding extending throughrespective ones of the apertures to individually link respective ones ofthe parallel flux paths.

References Cited in the file of this patent UNITED STATES PATENTS2,600,057 Kerns June 10, 1952 2,889,542 Goldner et al. June 2, 1959FOREIGN PATENTS 760,048 Great Britain Oct. 21, 1956 1,136,322 FranceDec. 29, 1956 1,141,472 France Mar. 18, 1957 1,187,894 France Oct. 29,1957

